Staying light

Currently running an old 1987 Mariner (Yamaha), pretty light, was getting around 28mph on a 1652 with tunnel.
The only issue is that it's noisy.
If I were to repower I think I'll stay around the 30hp range due to weight and the high 20s is fine for me in our small lakes,rivers.
Reason I'm ranting is that my boat can handle a 60hp but the weights is over double what I'm running now, for approximately what 6 -10 mph?
Guess I'm asking for every 5 mph you gain what...1 or 2 mph? and
Weight how much do you lose 1 or 2 mph? 100lbs 50lbs?
Plus draft, which I think will be the deciding factor, hard rocks, flooded timber and rivers and what I fish in mostly, my props are all in hard shape(I keep 2 spares in the boat)
Still curious on the gain or lose in mph due to increase mpx or weight gain...any reading on this anywhere.

Yes the current 4-stroke engines are a lot quieter than the older 2-stroke engines. Significantly quieter, and more fuel efficient as well. So the extra pounds you carry in engine might even be offset in fuel weight on longer journeys.

If you closely look at the engine specs, they're grouped by weight. Several hp ratings essentially use the same engine block and gear case, so you can maximize the horsepower and minimize the weight by going to the max hp of the group. For instance, with suzuki IIRC the 9.9, 15, and 20hp are the same engine with different computers and intakes. So you can have a heavy 9.9 or a light 20hp for the same weight. In theory, because the 9.9 is detuned, it should be under less stress and last longer. But in reality, the engines don't really break or wear out in normal use.

Some brands the 25-50hp are the same block. You'll need to research carefully and go over the specs.

Hope that helps,

- B

Zum said:

Currently running an old 1987 Mariner (Yamaha), pretty light, was getting around 28mph on a 1652 with tunnel.
The only issue is that it's noisy.
If I were to repower I think I'll stay around the 30hp range due to weight and the high 20s is fine for me in our small lakes,rivers.
Reason I'm ranting is that my boat can handle a 60hp but the weights is over double what I'm running now, for approximately what 6 -10 mph?
Guess I'm asking for every 5 mph you gain what...1 or 2 mph? and
Weight how much do you lose 1 or 2 mph? 100lbs 50lbs?
Plus draft, which I think will be the deciding factor, hard rocks, flooded timber and rivers and what I fish in mostly, my props are all in hard shape(I keep 2 spares in the boat)
Still curious on the gain or lose in mph due to increase mpx or weight gain...any reading on this anywhere.

Click to expand...

If you regularly run in "Hard Water" I would seriously consider a jet.

I went from 25 yamaha twin carb 2 stroke (105 lb) to four stroke yamaha 25 (129 lb) and actually picked up 2 mph and change. Same hull. Remove one motor, clamp the new one on (while still docked in 2 foot of water) then took off again. As close to apples-to-apples as I can think of.

If weight is a big deal, and you're carrying 6 gal of gas, consider going to a 3 gal tank--saves you some weight, helping offset the weight-gain by going to the newer 4 stroke.

I don't recall what the actual weight of the C25 Yamaha was (aka Mariner 25). I want to say around 115 lbs but I could be way off. It might be 155 or it might be 95, I can't remember for sure.

The older motors are old. They are used, and worn. A lot of them were also rated differently.

Agree on the jet. Problem with jet is flooded timber where there's a lot of leaves and debris in the water and on the bottom-has a tendency to plug the grate more often, forcing the operator to shut the engine off, let the stuff fall off, then restarting. Had one and thought it would be nice, and it was, as long as it was deep enough that the jet wasn't sucking the stuff up off the bottom. Happened mostly in neutral and reverse but sometimes in forward at lower speeds. Sand is another issue-doesn't stop up the intake but it does wear the impeller and sleeve quickly. But that's why they make stainless impellers and replaceable sleeves. They're also a little on the noisy side by design (exhaust out of the jet).